Stack Auth is a fully open-source authentication platform designed as a drop-in replacement for proprietary solutions like Auth0 and Clerk. Built with TypeScript and optimized for Next.js, it provides a complete user authentication and management system—including sign-in/up components, session handling, email workflows, and role-based access control—without vendor lock-in. Unlike commercial alternatives, Stack Auth allows you to self-host at any time and export your user data freely under MIT and AGPL licenses. It’s ideal for developers building SaaS platforms, multi-tenant applications, or any product requiring secure, scalable authentication with minimal setup time.
The platform unifies authentication, authorization, and user management into a single system with a dashboard, API-first design, and seamless frontend integration. Whether you’re building a startup MVP or an enterprise SaaS with 10k+ users, Stack Auth eliminates the need to build and maintain custom auth logic while retaining full control over your infrastructure.
What You Get
- <SignIn/> and <SignUp/> components - Pre-built, themeable React components supporting OAuth providers, email/password login, and magic links with automatic dark/light mode support.
- Idiomatic Next.js APIs - Built on server components, React hooks, and route handlers for seamless integration with modern Next.js applications without requiring external SDKs.
- User dashboard - A full-featured admin panel to filter, search, edit, and analyze users with real-time data visualization—replacing the need for custom internal tools.
- Account settings UI - Out-of-the-box interface for users to manage profile, verify email, and change passwords with no configuration required.
- Multi-tenancy & teams - Built-in organization structure to manage B2B customers with team-based access and scalable user segmentation up to millions of users.
- Role-Based Access Control (RBAC) - Define granular permissions and assign them to users or teams; organizations can create custom roles with hierarchical access rules.
- OAuth Connections - Manage third-party API access tokens (e.g., Google Calendar, Outlook) with automatic refresh and scope control—accessible via a single function call.
- Passkeys support - Enable passwordless authentication using WebAuthn-based passkeys with biometric or security key login across devices.
- Impersonation - Admins can log in as any user for debugging or customer support without needing their credentials.
- Webhooks - Event-driven notifications via Svix for user actions like sign-up, login, or profile updates to trigger downstream workflows.
- Automatic customizable emails - WYSIWYG email editor for templates on sign-up, password reset, and verification with full HTML/CSS control.
- Session & JWT management - Automatic handling of refresh tokens, access tokens, and secure cookies with optimal performance and no manual implementation.
- M2M authentication - Issue short-lived access tokens for machine-to-machine communication between microservices or backend systems.
Common Use Cases
- Building a multi-tenant SaaS dashboard with RBAC - A B2B platform serving multiple companies, where each organization needs isolated user roles and permissions—Stack Auth’s team-based RBAC eliminates custom auth code.
- Creating a passwordless SaaS app with passkeys - A modern web application aiming for frictionless login; Stack Auth enables biometric sign-in without requiring users to remember passwords.
- Replacing Auth0/Clerk in a self-hosted environment - A startup that outgrew cloud auth providers due to cost or compliance needs; Stack Auth allows full data ownership and migration without vendor lock-in.
- DevOps teams managing auth for microservices - Teams using Next.js frontends and Node.js backends need a unified auth layer; Stack Auth’s REST API and M2M tokens provide consistent authentication across services.
Under The Hood
The project is a modern, TypeScript-based authentication and management platform designed for SaaS environments, offering modular support for user permissions, API key handling, and OAuth integrations. It adopts a monorepo structure that cleanly separates backend logic from dashboard UI, enabling scalable and maintainable development.
Architecture
This system follows a modular architecture with distinct backend and frontend applications, emphasizing clear separation of concerns and extensible design patterns.
- The architecture leverages strategy and factory patterns for flexible OAuth provider handling
- Component-based UI composition supports scalable state management and reusability
- Well-defined layers separate authentication flows, database operations, and API interactions
- Strong emphasis on tenancy and permission systems for multi-user environments
Tech Stack
Built with TypeScript and Next.js, the project utilizes a modern ecosystem of tools and libraries to support full-stack development.
- Primary language is TypeScript, with Next.js powering both backend and frontend components
- Extensive use of Prisma for database operations and OpenID Connect for secure authentication
- Employs Vite, Turbo, and PNPM for efficient builds and dependency management
- Vitest is used for comprehensive test coverage with shared configuration across modules
Code Quality
The codebase reflects a mature approach to backend development with strong emphasis on error handling and structured data operations.
- Comprehensive CRUD support for API keys and user permissions with consistent error handling
- Clear separation between authentication logic, database interactions, and UI components
- Consistent use of custom error types alongside standard HTTP status codes for robust error management
- Strong linting and CI/CD configurations ensure code quality and maintainability
What Makes It Unique
This project stands out through its extensible and SaaS-ready authentication infrastructure, tailored for modern enterprise use cases.
- Offers a unified backend architecture that handles complex OAuth flows and multi-factor authentication
- Implements team-based permissions and tenancy support in a scalable, modular fashion
- Introduces practical innovations in database migration workflows and email delivery systems
- Provides a highly extensible foundation for SaaS platforms requiring robust user and access management